1. Technical Field
The present invention relates to a positive electrode active material for lithium ion batteries, a positive electrode for lithium ion batteries, and a lithium ion battery.
2. Related Art
In regard to the positive electrode active material for lithium ion batteries, lithium-containing transition metal oxides have been generally used. Specific examples thereof include lithium cobaltate (LiCoO2), lithium nickelate (LiNiO2), and lithium manganate (LiMn2O4), and in order to improve characteristics (an increase in capacity, cycle characteristics, storage characteristics, reduction of internal resistance, and rate characteristics) or to increase safety, compositization of these materials is in progress. Lithium ion batteries for large-sized applications such as for automobiles and for load leveling, are required to have characteristics that are different from batteries for mobile telephones or personal computers up to date.
For an improvement of battery characteristics, various methods have been hitherto used, and for example, Patent document 1 (Japanese Patent No. 4175026) discloses a method for producing a positive electrode material for lithium secondary batteries, the method including passing a lithium nickel composite oxide represented by the composition of:LixNi1-yMyO2-δwherein 0.8≦x≦1.3; 0<y≦0.5; M represents at least one element selected from the group consisting of cobalt (Co), manganese (Mn), iron (Fe), chromium (Cr), vanadium (V), titanium (Ti), copper (Cu), aluminum (Al), gallium (Ga), bismuth (Bi), tin (Sn), zinc (Zn), magnesium (Mg), germanium (Ge), niobium (Nb), tantalum (Ta), beryllium (Be), boron (B), calcium (Ca), scandium (Sc) and zirconium (Zr); δ corresponds to the amount of oxygen deficiency or oxygen excess, and represents −0.1<δ<0.1,
through a classifier, separating the composite oxide into particles having large particle sizes and particles having small particle sizes at an equilibrium separation particle size Dh=1 to 10 μm, and blending particles having large particle sizes with particles having small particle sizes at a weight ratio of 0:100 to 100:0. The Patent Literature recites that according to this method, a positive electrode material for lithium secondary batteries with various balances between rate characteristics and capacity can be easily manufactured.
Patent document 1: Japanese Patent No. 4175026